Semiconductor laser light source unit

ABSTRACT

A rod lens or a cylindrical lens is disposed in front of a semiconductor laser to increase a divergence angle of a laser beam emitted from the semiconductor laser so as to form a substantially circular far field pattern. In another constitution, there is disposed in front of a semiconductor laser a composite lens having two cylindrical surfaces whose cylindrical axes are perpendicular to each other. The cylindrical surface on the side of the semiconductor laser is a convex surface and the other cylindrical surface is a convex or concave surface. In still another constitution, two semiconductor lasers emitting the same optical signal are arranged adjacent each other so that respective light emitting portions of two pn junction planes are located in the same plane and perpendicular to each other, and that laser beams form orthogonal spots at a single predetermined position.

This application is a division of application Ser. No. 08/022,549, filedon Feb. 25, 1993 now U.S. Pat. No. 5,499,262.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor laser light source unitused for a remote control unit, an optical transmission unit, a unit forhigh-speed optical communication, etc.

Conventionally, a GaAs LED (wavelength: 950 nm) is used as a lightsource for a remote controller. While the GaAs LED has a rise time of 1μsec, an AlGaAs LED (wavelength: 850 nm), which has come to be used as alight source for high-speed optical signal transmission, has a shorterrise time of 0.3 μsec.

However, even the AlGaAs LED cannot be used to transmit a high-frequencysignal of more than 1 MHz. That is, the infrared light of the AlGaAs LEDcannot accommodate the spatial transmission of an audio-video signal andan optical signal for communication between computers, which signalsshould carry a large amount of information.

To accommodate such cases, a semiconductor laser, whose build up isfaster than the above-mentioned infrared LEDs and which enablestransmission of high-speed pulses, is now being given much attention.However, the divergence angle of a laser beam emitted from thesemiconductor laser depends on the angle around its axis, and the beamcross-section is elliptical rather than circular. More specifically, thelaser beam travels toward a light-receiving surface with itscross-section assuming an elliptical far field pattern (FFP) whosemajor-axis is perpendicular to the pn junction plane (hereinafter alsocalled "chip junction plane") of a laser chip.

Therefore, the laser beam can be directed easily so as to properlyilluminate a predetermined position in the major-axis direction of theelliptical pattern, but is hardly directed to the predetermined positionin the minor-axis direction (i.e., the direction in parallel with thechip junction plane) in which direction the light intensity distributionis too narrow. For example, when a device including a semiconductorlaser is installed, its positioning with respect to a light-receivingsurface is very difficult. In particular, such positioning by manualhandling is extremely difficult.

On the other hand, the angular half-width (full width at half maximum)of the light intensity distribution in the major-axis direction of theelliptical pattern (the cross-section perpendicular to the beam axis)varies over a wide range of 25° to 45°. As a result, a peripheral partof the laser beam cannot be utilized because its light intensity is toolow. For example, if the half-width of the light intensity distributionis in the 35°-45° range, the peripheral part of the beam has too lowintensity to be used in a remote controller.

As a countermeasure, the light output power of the semiconductor laserneeds to be increased to compensate for the unusable peripheral part ofthe beam. However, there arises a problem that high-light-outputsemiconductor lasers are expensive and have large electric powerconsumption. They are not suitable specifically for a battery-driven,handy terminal.

SUMMARY OF THE INVENTION

The present invention has been made to solve the above-describedproblems, and has an object of providing a semiconductor laser lightsource unit which enables easy setting of a laser beam direction as wellas high-speed transmission of a large amount of information. At the sametime, it is also intended to enable reduction of the light output powerby effectively utilizing a peripheral part of the laser beam.

Another object of the invention is to provide a low-cost semiconductorlaser light source unit which enables easy setting of a laser beamdirection as well as high-speed transmission of a large amount ofinformation.

According to a first aspect of the invention, a semiconductor laserlight source unit comprises:

a semiconductor laser for emitting a laser beam having an ellipticalsectional shape; and

optical means for increasing a divergence angle of the laser beam in adirection parallel with a minor-axis of the elliptical sectional shapeso as to produce a substantially circular far field pattern of the laserbeam.

with the above constitution, the divergence angle of the laser beamloses dependence on the angle around its axis, and isotropicillumination can be attained.

According to a second aspect of the invention, a semiconductor laserlight source unit comprises:

a semiconductor laser for emitting a laser beam having an ellipticalsectional shape; and

a lens comprising a first cylindrical surface having a first cylindricalaxis that is in parallel with a minor-axis of the elliptical sectionalshape for decreasing a first divergence angle of the laser beam in adirection of a major-axis of the elliptical sectional shape, and asecond cylindrical surface having a second cylindrical axis that is inparallel with the major-axis of the elliptical sectional shape forincreasing a second spreading angle of the laser beam in a direction ofthe minor-axis of the elliptical sectional shape.

With the above constitution, since the beam divergence angle isdecreased in the direction parallel with the major-axis of theelliptical sectional shape, it becomes possible to reduce the proportionof an unusable peripheral part of the laser beam. Further, the provisionof the circular far field pattern enables isotropic illumination.

According to a third aspect of the invention, in a semiconductor laserlight source unit, a plurality of semiconductor lasers are arrangedadjacent each other so that light emitting portions of respective chipjunction planes are not in parallel with each other, and emit respectivelaser beams carrying the same signal toward a single predeterminedposition.

With the above constitution, a plurality of light spots are formed atthe single predetermined position to produce a less anisotropic patternthere.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view schematically showing a semiconductor laserlight source unit according to a first embodiment of the presentinvention;

FIG. 2 is a light path diagram in the YZ-plane;

FIG. 3 is a light path diagram in the ZX-plane;

FIG. 4 is a graph showing a directivity in the YZ-plane;

FIG. 5 is a graph showing a directivity in the ZX-plane;

FIG. 6 is a perspective view schematically showing a semiconductor laserlight source unit according to a second embodiment of the invention;

FIG. 7 is a perspective view schematically showing a semiconductor laserlight source unit according to a third embodiment of the invention;

FIG. 8 is a perspective view showing an appearance of a lens used in thethird embodiment;

FIG. 9 is a perspective view schematically showing a semiconductor laserlight source unit according to a fourth embodiment of the invention;

FIG. 10 is a perspective view showing an appearance of a lens used inthe fourth embodiment;

FIG. 11 is a perspective view showing an appearance of a lens used infifth embodiment;

FIG. 12 is a perspective view showing an appearance of a lens used in asixth embodiment;

FIG. 13 is a graph showing a light intensity distribution in theX-direction in the third to sixth embodiments;

FIG. 14 is a diagram showing a light path in the end portion of the lensused in the fifth and sixth embodiments;

FIG. 15 is a perspective view schematically showing a semiconductorlaser light source unit according to a seventh embodiment of theinvention; and

FIG. 16 shows a cruciform pattern formed by two laser beams in theseventh embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention are described hereinafter withreference to the accompanying drawings. In the following description, itis assumed in the drawings that the cross-section of a laser beam is inthe XY-plane (stated more strictly, in a plane parallel with theXY-plane as defined by the coordinate system indicated in the figures).

FIG. 1 is a perspective view schematically showing constitution of alight source unit according to a first embodiment of the invention,which mainly consists of a semiconductor laser 10, a rod lens 20 and abody 30 (only the outline of which is indicated by the chain line inFIG. 1).

The semiconductor laser 10 is of a general, package-type laser diode inwhich a laser chip is hermetically sealed in a can. A single laser chip(indicated by reference numeral 15 in FIG. 3) emitting a single laserbeam LB (wavelength: 780 nm) is provided in the semiconductor laser 10.The laser beam LB is emitted from the cleavage surface toward apredetermined position, i.e., along the Z-direction. The rod lens 20 isa circular rod lens having a constant diameter in its axial direction100. The head of the semiconductor laser 10 is inserted into and fixedto the box-shaped body 30. The end faces of the rod lens 20 are fixed tothe inner wall of the body 30.

The semiconductor laser 10 and the rod lens 20 are positioned to eachother in the following manner. First, while the pn junction plane of thelaser chip 15 of the semiconductor laser 10 is placed in the YZ-plane,the central axis of the emitted laser beam LB is positioned along theZ-axis. As a result, a sectional pattern P₁ of the laser beam LB assumesan elliptical shape whose major-axis extends along the X-direction. Onthe other hand, the rod lens 20 is positioned so that its axis 100becomes in parallel with the X-direction.

After passing through the rod lens 20, the sectional pattern of thelaser beam LB is changed to a circular pattern P₂. FIGS. 2 and 3 showpaths of the laser beam LB in the YZ- and ZX planes, respectively. Inthe YZ-plane, light rays entering the rod lens 20 at incident angles1.5°, 3.5° and 5° exit therefrom at exit angles 7.5°, 15.5° and 28°,respectively to spread. On the other hand, in the ZX-plane where the rodlens 20 has no curvature, there exist only slight path variations. If itis assumed that the light rays having 100% light intensity enter the rodlens 20 at incident angles 1.5°, 3.5° and 5°, they exit therefrom withintensities 95%, 60% and 40%, respectively.

FIGS. 4 and 5 (solid lines) show directivities in the Y- andX-directions, respectively of the laser beam LB emitted from the lightsource unit of this embodiment. It is understood that the directivity inthe Y-direction is equivalent to that in the X-direction, on which therod lens 20 has almost no influences. Further, the directivity in theY-direction is almost equal to a directivity of an infrared LED, whichis indicated by the chain line in FIG. 4.

According to this embodiment, after passing through the rod lens 20, thesectional pattern of the laser beam LB is changed to the circularpattern P₂ having half-value angles ±15° that is suitable for a remotenetwork etc. Since the signal-detectable range is extended in thedirection in parallel with the pn junction plane, the beam direction canbe set easily.

In the case of conventional infrared LED light sources, it is difficultto converge, by an optical system, the laser beam to form a small spoton a p-i-n photodiode that constitutes a light-receiving surface.Therefore, a large p-i-n photodiode is employed conventionally, whichhowever is associated with a problem of large background noise. In thisembodiment, on the other hand, since the laser beam can easily beconverged into a small spot, it becomes possible to employ a small p-i-nphotodiode and, as a result, the SN ratio can be improved.

Further, enabling isotropic, wide-range illumination, the light sourceunit of this embodiment can also be applied to a field in whichdivergent light from a semiconductor laser is used, for instance, asinfrared illumination light in a CCD camera burglar prevention system.

FIG. 6 shows a light source unit according to a second embodiment of theinvention. This embodiment has the same constitution as the firstembodiment except that the rod lens 20 is replaced by a cylindrical lens25, and can provide the same advantages as the first embodiment.

The cylindrical lens 25 is positioned so that its axis 200 becomes inparallel with the X-direction. One surface of the cylindrical lens 25 onthe side of the semiconductor laser 10 is a plane in parallel with theXY plane, and the other surface on the side of the laser beam output isa concave cylindrical surface, which has no curvature along theX-direction.

As in the case of the first embodiment, before passing through thecylindrical lens 25 the laser beam LB has an elliptical sectionalpattern P₃ whose major-axis extends along the X-direction (radius r_(x)>r_(y)). After passing through the cylindrical lens 25, the sectionalpattern of the laser beam LB is changed to a circular pattern P₄ (radiusR_(x) =R_(y)). Therefore, the directivity in the Y-direction isexpanded, like the case of the first embodiment.

While in FIG. 6 a concave surface is provided only on one side of thecylindrical lens 25, other types of cylindrical lenses may be used. Aconvex surface may be provided only on one side or on both sides, or aconcave surface may be provided on both sides to form a cylindricallens. Where the cylindrical lens has a concave surface(s), the laserbeam LB is directly diverged. On the other hand, where the cylindricallens has a convex surface(s), the laser beam LB converges and spreadsthereafter, like the case of the rod lens 20 of the first embodiment(see FIG. 2).

FIG. 7 is a perspective view schematically showing constitution of alight source unit according to a third embodiment of the invention, andFIG. 8 is a perspective view showing an appearance of a lens 120 used inthe light source unit of FIG. 7. The light source unit of thisembodiment mainly consists of a semiconductor laser 10, the lens 120 anda body 150 (only the outline of which is indicated by the chain line inFIG. 7). The semiconductor laser 10 and the lens 120 are fixed to thebody 150.

The semiconductor laser 10 is of a general, package-type laser diode inwhich a laser chip (not shown) is hermetically sealed in a can. A singlelaser chip emitting a single laser beam LB (wavelength: 780 nm) isprovided in the semiconductor laser 10. The laser beam LB is emittedfrom the cleavage surface toward a predetermined position, i.e., alongthe Z-direction.

The lens 120 serves to correct the light intensity distribution of thelaser light LB, and has a structure in which two cylindrical lenses arejoined together such that their axes are perpendicular to each other.One cylindrical lens whose axis extends along the Y-direction has afirst cylindrical surface S₁ on the side of the semiconductor laser 10.The other lens whose axis extends along the X-direction has a secondcylindrical surface S₂ on the side of the laser beam output.

The first cylindrical surface S₁ has the cylindrical axis that is inparallel with the Y-axis, i.e., perpendicular to the major-axis r_(x) ofa far field pattern P₃ of the laser beam LB, and serves to decrease thedivergence angle of the laser beam LB in the ZX-plane from θ₁ to θ₂. Thesecond cylindrical surface S₂ has the cylindrical axis that is inparallel with the X-axis, i.e., perpendicular to the cylindrical axis ofthe first cylindrical surface S₁, and serves to increase the divergenceangle in the YZ-plane from α₁ to α₂.

The head of the semiconductor laser 10 is inserted into and fixed to thebox-shaped body 150. The end faces of the lens 120 are fixed to theinner wall of the body 150.

The semiconductor laser 10 and the lens 120 are positioned to each otherin the following manner. First, while the pn junction plane of the laserchip of the semiconductor laser 10 is placed in the YZ-plane, thecentral axis of the emitted laser beam LB is positioned along theZ-axis. As a result, a far field pattern P₃ of the laser beam LB assumesan elliptical shape whose major-axis extends along the X-direction. Onthe other hand, the cylindrical axis of the second cylindrical surfaceS₂ of the lens 120 is positioned along the X-direction.

In the direction parallel with the Y-direction, by passing through thelens 120, the laser beam 120 once converges and then spreads to increaseits divergence angle (α₁ <α₂). In the direction parallel with theX-direction, the divergence angle of the laser beam LB is reduced (θ₁>θ₂). For example, θ₁ and θ₂ are 45° and 20°, respectively. As a result,the far field pattern changes from the elliptical pattern P₃ to thecircular pattern P₄ that is suitable, for instance, for a remotenetwork. In FIG. 7, R_(x) and R_(y) correspond to r_(x) and r_(y),respectively. With the above constitution, the signal detection range isexpanded in the direction parallel with the pn junction plane, enablingeasy setting of the beam direction.

FIG. 13 shows light intensity distributions along the X-direction of thefar field patterns P₃ (solid line) and P₄ (chain line). As is seen fromthis figure, the peripheral part of the light intensity distribution,which was not utilized actually before the invention, is now locatedwithin the divergence angle range of ±20°. Therefore, the peripheralpart of the laser beam LB can be utilized effectively to equivalentlyincrease the light intensity. It becomes possible to reduce the lightoutput power.

In the case of conventional infrared LED light sources, it is difficultto converge, by an optical system, the laser beam to form a small spoton a p-i-n photodiode that constitutes a light-receiving surface.Therefore, a large p-i-n photodiode is employed conventionally, whichhowever is associated with a problem of large background noise. In thisembodiment, on the other hand, since the laser beam can easily beconverged into a small spot, it becomes possible to employ a small p-i-nphotodiode and, as a result, the SN ratio can be improved.

Further, enabling isotropic, wide-range illumination, the light sourceunit of this embodiment can also be applied to a field in whichdivergent light from a semiconductor laser is used, for instance, asinfrared illumination of CCD camera burglar prevention system.

FIG. 9 is a perspective view schematically showing constitution of alight source unit according to a fourth embodiment of the invention, andFIG. 10 is a perspective view showing an appearance of a lens 125 usedin the light source unit of FIG. 9. This embodiment has the sameconstitution as the third embodiment except that the lens 120 isreplaced by a lens 125, and can provide the same advantages as the thirdembodiment. That is, while in the third embodiment the secondcylindrical surface S₂ on the side of the laser beam output is a convexsurface, in the lens 125 of this embodiment a second cylindrical surfaceS₄ on the beam output side is a concave surface.

Like the far field pattern P₃ of the third embodiment, a far fieldpattern P₅ of the laser beam LB before reaching the lens 125 assumes anelliptical shape whose major-axis extends along the X-direction (r_(x)>r_(y)). By passing through the lens 125, the laser beam LB diverges inthe Y-direction to increase its divergence angle (α₃ <α₄). On the otherhand, the divergence angle of the laser beam LB is reduced (θ₃ >θ₄). Forexample, θ₃ and θ₄ are 45° and 20°, respectively. As a result, the farfield pattern changes from the elliptical pattern P₅ to the circularpattern P₆ that is suitable, for instance, for a remote network. In FIG.9, R_(x) and R_(y) correspond to r_(x) and r_(y), respectively. With theabove constitution, as in the case of the third embodiment, the signaldetection range is expanded in the direction parallel with the pnjunction plane, enabling easy setting of the beam direction.

In the third and fourth embodiments, if the portion of the firstcylindrical surface S₁ or S₃ that receives the peripheral part of thefar field pattern P₃ or P₅ has a curvature larger than that of thecentral portion, the light intensity distribution in the X-direction ofthe far field pattern P₄ or P₆ can be made flatter.

FIG. 11 is a perspective view showing an appearance of a lens 130 usedin a light source unit according to a fifth embodiment of the invention.The lens 130 has a plane F₁ that is formed by cutting the firstcylindrical surface S₁ of the lens 120 of the third embodiment by aplane in parallel with the XY-plane to remove its central portion. Withthis lens 130, the divergence angle of only the peripheral part of thelaser beam LB is reduced in the X-direction by the cylindrical surfacesS_(a) and S_(b) that are the same as the first cylindrical surface S₁ ofthe lens 120. The spread of the peripheral part of the light intensitydistribution can be changed as desired by adjusting the size of theplane F₁.

FIG. 12 is a perspective view showing an appearance of a lens 135 usedin a light source unit according to a sixth embodiment of the invention.The lens 135 has a plane F₂ that is formed by cutting the firstcylindrical surface S₃ of the lens 125 of the fourth embodiment by aplane in parallel with the XY-plane to remove its central portion. Withthis lens 135, the divergence angle of only the peripheral part of thelaser beam LB is reduced in the X-direction by the cylindrical surfacesS_(c) and S_(d) that are the same as the first cylindrical surface S₃ ofthe lens 125. The spread of the peripheral part of the light intensitydistribution can be changed as desired by adjusting the size of theplane F₂.

FIG. 13 also shows, by the chain double-dashed line, a light intensitydistribution in the X-direction of the far field pattern formed in thefifth or sixth embodiment. Like the case of the third and fourthembodiments, the peripheral part of the light intensity distribution,which was not utilized actually before this invention, is now locatedwithin the divergence angle range of ±20°. In addition, the lightintensity distribution in the X-direction of the far field patternbecomes flatter to enable more uniform illumination of thelight-receiving surface.

FIG. 14 shows a light path at the end portion of the lens 130 used inthe fifth embodiment. Since the divergence angle of the laser beam LB isreduced by the surface S_(a), in this end portion the lens 130 can beshorter, by a length d, than the case of a flat surface indicated by thechain line. The third, fourth and sixth embodiments can also provide thesame advantage.

FIG. 15 is a perspective view schematically showing a light source unitaccording to a seventh embodiment of the invention. A light source unit200 mainly consists of two semiconductor lasers 10 and a fixing member240 (only the outline of which is indicated by the chain line in FIG.15). The two semiconductor lasers 10 are fixed to the member 240. Eachsemiconductor laser 10 is of a general, package-type laser diode inwhich a laser chip 220 is hermetically sealed in a can. A single laserchip 220 emitting a single laser beam (wavelength: 780 nm) is providedin each semiconductor laser 10. The laser beams are emitted from the pnjunction planes 225 of the laser chips 220 toward the same predeterminedposition, i.e., along the Z-direction. Since the respectivesemiconductor lasers 10 are connected to a power source in parallel soas to be on/off-controlled synchronously, they emit the same signalconcurrently.

Two through holes 230 are provided in the fixing member 240. The headsof the semiconductor lasers 10 are inserted into and fixed to therespective through holes 230 to form the light source unit 200. The twothrough holes 230 are formed in parallel with each other, and theposition of the beam emitting portion of each pn junction plane 225 isadjusted on the center line of the corresponding through hole 230 toprevent interruption of the diverging laser beam.

The semiconductor lasers 10 are arranged and fixed so that the beamemitting portions of the pn junction planes 225 of the respective laserchips 220 are orthogonal. That is, in this embodiment, the pn junctionplane 225 of one laser chip 220 is located in the YZ-plane, and the pnjunction plane 225 of the other laser chip 220 is located in theZX-plane. Both beams are emitted along the Z-direction.

Since the laser beams emitted from the pn junction planes 225 have anelliptical sectional shape whose major-axis extends in the directionperpendicular to the pn junction plane 225, they travel toward alight-receiving surface located at a predetermined position with theircross-sections assuming an elliptical far field pattern. As a result, asshown in FIG. 16, two orthogonal spots P₇ and P₈ are formed on the samepredetermined position by the respective beams to produce a cruciformpattern. The two beams can be emitted along the Z-direction as mentionedabove, i.e., need not be inclined, because the predetermined position ofthe light-receiving surface is usually very far from the light sourceunit compared to the beam interval. If the diameter of the semiconductorlasers 10 is 5.6 mm, a practical value of their interval is about 10 mm.

If it is assumed that the detectable range, in terms of the beamdivergence angle, of one semiconductor laser 10 is ±30°-40° in thedirection perpendicular to the pn junction plane 225 and ±10°-15° in thedirection parallel therewith, the light source unit of the invention canimprove the latter detectable range to ±30°-40°.

Although in the above embodiment one package of the semiconductor laser10 contains only one laser chip 220, there may be employed another typeof semiconductor laser in which one package contains two or more laserchips. Although in the above embodiment the two semiconductor lasers 10are fixed to the single fixing member 240, three or more semiconductorlasers 10 may be employed. If the beam emitting portions of the pnjunction planes 225 are not in parallel with each other, the spotsformed at the same predetermined position cross each other. Therefore, apattern closer to the circular pattern than the cruciform pattern ofFIG. 16 can be produced by arranging three or more laser chips 220 inthe XY-plane at proper angles.

According to the seventh embodiment, the signal detectable range can beincreased in the direction parallel with the pn junction plane 225 tothereby facilitate setting of the beam direction. Further, since twosemiconductor lasers are less expensive than one lens, the light sourceunit of this embodiment can be produced at a lower cost than the case ofusing a lens. In the case of conventional infrared LED light sources, itis difficult to converge, by an optical system, the laser beam to form asmall spot on a p-i-n photodiode that constitutes a light-receivingsurface. Therefore, a large p-i-n photodiode is employed conventionally,which however is associated with a problem of large background noise. Inthis embodiment, on the other hand, since the laser beam can easily beconverged into a small spot, it becomes possible to employ a small p-i-nphotodiode and, as a result, the SN ratio can be improved.

According to the invention, as described above by way of the first andsecond embodiments, the use of the semiconductor laser enablestransmission of a large amount of information at high speed. By virtueof the provision of the optical system (e.g., a rod lens or cylindricallens) for diverging or converging the laser beam emitted from thesemiconductor laser so as to produce a circular sectional shape, thedirection of the laser beam can be set easily. As a result, a deviceincluding a semiconductor laser can easily be positioned with respect toa light-receiving surface when it is installed. This advantage is moreremarkable when the device needs to be positioned manually.

Further, since the circular sectional shape of the laser beam enablesisotropic, wide-range illumination, the semiconductor laser light sourceunit of the invention is applicable to dark field illumination forsecurity purposes.

According to the invention, as described above by way of the third tosixth embodiments, the use of the semiconductor laser enablestransmission of a large amount of information at high speed. By virtueof the provision of the lens having two cylindrical surfaces whose axesare arranged perpendicularly to each other, it becomes possible toeffectively utilize the peripheral part of the laser beam, and to reducethe light output power. Further, the direction of the laser beam can beset easily.

By lowering the light output power, the efficiency of power utilizationcan be improved by more than 30%. Where the portion of the firstcylindrical surface that receives the peripheral part of the far fieldpattern has a curvature larger than the central portion (for example,the peripheral portion is a curved surface and the central portion is aflat surface), the light intensity distribution with respect to the beamdivergence angle becomes flatter to enable more uniform illumination ofthe light-receiving surface.

Since the first cylindrical surface can decrease the beam divergenceangle in the major-axis direction of the far field pattern, the lengthof the lens can be reduced accordingly. As a result, the light sourceunit can be made more compact.

Since the direction of the laser beam can be set easily, a deviceincluding a semiconductor laser can easily be positioned with respect toa light-receiving surface when it is installed. This advantage is moreremarkable when the device needs to be positioned manually.

Further, since the circular sectional shape of the laser beam enablesisotropic, wide-range illumination, the semiconductor laser light sourceunit of the invention is applicable to dark field illumination forsecurity purposes.

According to the invention as described above by way of the seventhembodiment, high-speed transmission of a large amount of informationbecomes possible by using the laser chips having the pn junction planesfrom which the laser beams are emitted toward the same predeterminedposition. The direction of the beams can be set easily by arranging atleast two laser chips so that the beam emitting portions of the pnjunction planes are not in parallel with each other. Further, the costreduction can be attained by virtue of unnecessariness of using anexpensive optical system. In particular, the setting of the beamdirection can be facilitated by orthogonally arranging the beam emittingportions of the two laser chips.

What is claimed is:
 1. A semiconductor laser light source unit forilluminating a remote light-receiving surface comprising a plurality ofsemiconductor lasers, each laser being contained in a separate package,the lasers being arranged adjacent to each other so as to emit lightbeams along the same axis toward the remote light-receiving surface andbeing oriented so that light emitting portions of respective pn junctionplanes are not parallel with each other and the light beams provide anillumination pattern on the light-receiving surface having improvedangular uniformity, and wherein the semiconductor lasers emit respectivelaser beams carrying the same signal toward a single predeterminedposition at the remote light receiving surface.
 2. The semiconductorlaser light source unit of claim 1, wherein the plurality ofsemiconductor lasers are two semiconductor lasers having the respectivelight emitting portions that are arranged perpendicularly to each other.3. A semiconductor laser light source unit according to claim 1, whereinthe light beams from the plurality of semiconductor lasers cross eachother at a selected location on the remote light-receiving surface. 4.The semiconductor laser light source unit of claim 3, wherein theplurality of semiconductor lasers are two semiconductor lasers, and thelaser beams emitted from the two semiconductor lasers have ellipticalshapes that are orthogonal at the selected location.